Heart disease and zebrafish

The zebrafish - which can mend its own heart muscle - is providing clues to heart failure, which affects 750,000 people in the UK. Heart failure results in the heart pumping blood incorrectly and in insufficient amounts throughout the body. A heart attack is often a cause of heart muscle death, which is in turn a large contributor to disability.

Zebrafish are important to biomedical science and have increasingly become the research animal of choice. They have a fully functioning, simple heart and circulatory system that is easy to study because they are semi-transparent. Additionally, if part of a zebrafish’s heart is removed, they can grow it back in a matter of weeks. Scientists are working to find out what specific factors enable zebrafish to regenerate damaged tissue in the hope that this can be applied to humans. The ability to repair damaged heart tissue could lead to a vast increase in quality of life for people who have damaged hearts, coronary artery disease, high blood pressure or diabetes.

Researchers recently identified a molecule that tells certain stem cells in the zebrafish embryo whether to become either heart muscle or blood vessel cells. This molecule – called Fibroblast growth factor (Fgf) – may be the evolutionary switch that triggered four-chambered human hearts, from the two-chambered ‘tube-heart’ found in fish. Fgf is a multifunctional protein that has many different roles in humans including blood vessel development and wound healing.

The hope is that the Fgf switch can prompt stem cells to create brand new heart muscle in people with heart failure. The next stage in transferring the valuable zebrafish results to humans is to identify how genetic switches in the correct cells can be turned on or off to enable development of new heart cells. In the laboratory, the research will help the production of stem cells for use in heart repair.

Fgf has also been shown to stimulate growth of blood vessels in the heart after injury in rodent models. The findings of this study that cardiac cells can be induced to regenerate rather than produce scar tissue in the heart has important implications for the treatment of human heart failure.